Unlike Its Paralog LEDGF/p75, HRP-2 Is Dispensable for MLL-R Leukemogenesis but Important for Leukemic Cell Survival

Exome-wide association study reveals 7 functional variants associated with ex-vivo drug response in acute myeloid leukemia patients

Acute myeloid leukemia (AML) is an aggressive blood cancer characterized by poor survival outcomes. Further, due to the extreme molecular heterogeneity of the disease, drug treatment response varies from patient to patient. The variability of drug response can cause unnecessary treatment in more than half of the patients with no or partial therapy responses leading to severe side effects, monetary as well as time loss. Understanding the genetic risk factors underlying the drug response in AML can help with improved prediction of treatment responses and identification of biomarkers in addition to mechanistic insights to monitor treatment response. Here, we report the results of the first Exome-Wide Association Study (EWAS) of ex-vivo drug response performed to date with 175 AML cases and 47 drugs. We used information from 55,423 germline exonic SNPs to perform the analysis. We identified exome-wide significant (p < 9.02 × 10- 7) associations for rs113985677 in CCIN with tamoxifen response, rs115400838 in TRMT5 with idelalisib response, rs11878277 in HDGFL2 with entinostat, and rs2229092 in LTA associated with vorinostat response. Further, using multivariate genome-wide association analysis, we identified the association of rs11556165 in ATRAID, and rs11236938 in TSKU with the combined response of all 47 drugs and 29 nonchemotherapy drugs at the genome-wide significance level (p < 5 × 10- 8). Additionally, a significant association of rs35704242 in NIBAN1 was associated with the combined response for nonchemotherapy medicines (p = 2.51 × 10- 8), and BI.2536, gefitinib, and belinostat were identified as the central traits. Our study represents the first EWAS to date on ex-vivo drug response in AML and reports 7 new associated loci that help to understand the anticancer drug response in AML patients.

HRP2 regulating MICU1-mediated Ca2+ overload to dictate chemoresistance of multiple myeloma

Despite the efficacy of bortezomib (BTZ)-based chemotherapy in treating multiple myeloma (MM) patients, chemoresistance occurs frequently over time, particularly in individuals exhibiting an initial positive response to BTZ therapy. In this study, we established BTZ-resistant MM cells and identified that suppressed expression of the hepatoma-derived growth factor (HDGF)-related protein-2 (HRP2) was a key determinant of chemoresistance in MM cells. Manipulating HRP2 expression remodeled the chemosensitivity of MM cells in vitro and in vivo. Clinically, lower expression of HRP2 predicted a shorter survival rate in MM patients receiving BTZ-based regimens. Mechanistically, HRP2 depletion resulted in elevated acetylation modifications of histone 3 at lysine 27 (H3K27Ac), and enhanced chromatin accessibility as well as transcriptional elongation of mitochondrial calcium uptake 1(MICU1) gene, thus promoting the expression of MICU1 gene and alleviating calcium (Ca2+) overload and excessive reactive oxygen species (ROS) induced mitochondria damage and apoptosis in MM cells. Thereby, MICU1 suppression improved BTZ sensitivity in vitro and relieved tumor burden in a mouse model of MM. Similarly, elevated MICU1 expression was observed in the B220+CD19+ B cells from HRP2-knockout mice and significantly correlated with poor prognosis in the clinic. Thus, our study elucidates the previously unrecognized epigenetic role of HRP2 in regulating calcium homeostasis of MM cells, providing new theoretical insights into the mechanisms underlying the development of drug resistance in multiple myeloma.

Mechanistic insights into the phosphorylation-regulated a disordered protein interaction module

The TFIIS N-terminal domain (TND) is a crucial protein scaffold that selectively recognizes disordered ligands, known as TND-interacting motifs (TIMs). Understanding the specific mechanisms of TND-TIM interactions is essential for deciphering the transcription machinery. Here, we investigated the conformational ensembles of the TND-TIM interaction module using molecular dynamics simulations. The study revealed that the experimental structures of TND-TIM complexes, including P75-PogZ and P75-IWS1, maintained stable conformations during microsecond-long simulations, even when the linked proteins between TND and TIM were removed or when TIM was phosphorylated. Conversely, both P75-ASK and HRP2-IWS1, prepared based on the structure of P75-IWS1, are unstable in simulations; for example, the helix-1 of TIMs shifts from their initial binding site on TND. However, phosphorylation enhances TND-TIM interactions and rapidly stabilizes the complex structure. A general rule for phosphorylation regulation of TND-TIM interactions is identified: the phosphoryl group of TIM forms hydrogen bonds with the positively charged side chains of TND residues, promoting dynamic correlation between TND and the Ser-containing acidic linker of TIM, and enhancing residue-residue interactions among helix-1 and FXGF motif of TIM with TND. These phosphorylation-induced changes resulted in a higher affinity between TND and TIM. Our study provides insights into the phosphorylation-regulated TND-TIM interaction module at an atomic level, facilitating a deeper understanding of the molecular mechanisms of protein interactome assembly in transcription machinery.

Role of LEDGF/p75 (PSIP1) in oncogenesis. Insights in molecular mechanism and therapeutic potential

Aberrant gene expression due to dysfunction in proteins involved in transcriptional regulation is a hallmark of tumor development. Indeed, targeting transcriptional regulators represents an emerging approach in cancer therapeutics. Lens epithelium-derived growth factor (LEDGF/p75, PSIP1) is a co-transcriptional activator that tethers several proteins to the chromatin. LEDGF/p75 has been implicated in diseases such as HIV infection and KMT2A-rearranged leukemia. Notably, LEDGF/p75 is upregulated in various human cancers including prostate and breast cancer. In this review, we discuss the essential role of LEDGF/p75 in different malignancies and explore its mechanistic contribution to tumorigenesis revealing its potential as a therapeutic target for chemotherapy.

The Emerging Roles of the Stress Epigenetic Reader LEDGF/p75 in Cancer Biology and Therapy Resistance: Mechanisms and Targeting Opportunities

The lens epithelium derived growth factor of 75 kD (LEDGF/p75) is a transcription co-activator and epigenetic reader that has emerged as a stress oncoprotein in multiple human cancers. Growing evidence indicates that it promotes tumor cell survival against certain therapeutic drugs. The amino (N)-terminal region of LEDGF/p75 contains a PWWP domain that reads methylated histone marks, critical for recognizing transcriptionally active chromatin sites. Its carboxyl (C)-terminus has an integrase binding domain (IBD) that serves as the binding site for the HIV-1 integrase and multiple oncogenic transcription factors. Acting as hubs for protein-protein interactions, both domains facilitate the tethering of oncogenic transcription factors and regulators to active chromatin to regulate mRNA splicing, promote DNA repair, and enhance the expression of stress and cancer-related genes that contribute to tumor cell aggressiveness and chemoresistance. This review summarizes our current knowledge of the emerging roles of LEDGF/p75 in cancer biology and therapy resistance and discusses its potential as a novel oncotherapeutic target in combinatorial treatments.

Fragment-based discovery of small molecule inhibitors of the HDGFRP2 PWWP domain

The PWWP domain of hepatoma-derived growth factor-related protein 2 (HDGFRP2) recognizes methylated histones to initiate the recruitment of homologous recombination repair proteins to damaged silent genes. The combined depletion of HDGFRP2 and its paralog PSIP1 effectively impedes the onset and progression of diffuse intrinsic pontine glioma (DIPG). Here, we discovered varenicline and 4-(4-bromo-1H-pyrazol-3-yl) pyridine (BPP) as inhibitors of the HDGFRP2 PWWP domain through a fragment-based screening method. The complex crystal structures reveal that both Varenicline and BPP engage with the aromatic cage of the HDGFRP2 PWWP domain, albeit via unique binding mechanisms. Notably, BPP represents the first single-digit micromolar inhibitor of the HDGFRP2 PWWP domain with a high ligand efficiency. As a dual inhibitor targeting both HDGFRP2 and PSIP1 PWWP domains, BPP offers an exceptional foundation for further optimization into a chemical tool to dissect the synergetic function of HDGFRP2 and PSIP1 in DIPG pathogenesis.

Glucocorticoid Receptor Regulates and Interacts with LEDGF/p75 to Promote Docetaxel Resistance in Prostate Cancer Cells

Patients with advanced prostate cancer (PCa) invariably develop resistance to anti-androgen therapy and taxane-based chemotherapy. Glucocorticoid receptor (GR) has been implicated in PCa therapy resistance; however, the mechanisms underlying GR-mediated chemoresistance remain unclear. Lens epithelium-derived growth factor p75 (LEDGF/p75, also known as PSIP1 and DFS70) is a glucocorticoid-induced transcription co-activator implicated in cancer chemoresistance. We investigated the contribution of the GR-LEDGF/p75 axis to docetaxel (DTX)-resistance in PCa cells. GR silencing in DTX-sensitive and -resistant PCa cells decreased LEDGF/p75 expression, and GR upregulation in enzalutamide-resistant cells correlated with increased LEDGF/p75 expression. ChIP-sequencing revealed GR binding sites in the LEDGF/p75 promoter. STRING protein-protein interaction analysis indicated that GR and LEDGF/p75 belong to the same transcriptional network, and immunochemical studies demonstrated their co-immunoprecipitation and co-localization in DTX-resistant cells. The GR modulators exicorilant and relacorilant increased the sensitivity of chemoresistant PCa cells to DTX-induced cell death, and this effect was more pronounced upon LEDGF/p75 silencing. RNA-sequencing of DTX-resistant cells with GR or LEDGF/p75 knockdown revealed a transcriptomic overlap targeting signaling pathways associated with cell survival and proliferation, cancer, and therapy resistance. These studies implicate the GR-LEDGF/p75 axis in PCa therapy resistance and provide a pre-clinical rationale for developing novel therapeutic strategies for advanced PCa.

The TFIIS N-terminal domain (TND): a transcription assembly module at the interface of order and disorder

Interaction scaffolds that selectively recognize disordered protein strongly shape protein interactomes. An important scaffold of this type that contributes to transcription is the TFIIS N-terminal domain (TND). The TND is a five-helical bundle that has no known enzymatic activity, but instead selectively reads intrinsically disordered sequences of other proteins. Here, we review the structural and functional properties of TNDs and their cognate disordered ligands known as TND-interacting motifs (TIMs). TNDs or TIMs are found in prominent members of the transcription machinery, including TFIIS, super elongation complex, SWI/SNF, Mediator, IWS1, SPT6, PP1-PNUTS phosphatase, elongin, H3K36me3 readers, the transcription factor MYC, and others. We also review how the TND interactome contributes to the regulation of transcription. Because the TND is the most significantly enriched fold among transcription elongation regulators, TND- and TIM-driven interactions have widespread roles in the regulation of many transcriptional processes.

The Nuclear Dense Fine Speckled (DFS) Immunofluorescence Pattern: Not All Roads Lead to DFS70/LEDGFp75

The monospecific dense fine speckled (DFS) immunofluorescence assay (IFA) pattern is considered a potential marker to aid in exclusion of antinuclear antibody (ANA)-associated rheumatic diseases (AARD). This pattern is typically produced by autoantibodies against transcription co-activator DFS70/LEDGFp75, which are frequently found in healthy individuals and patients with miscellaneous inflammatory conditions. In AARD patients, these antibodies usually co-exist with disease-associated ANAs. Previous studies reported the occurrence of monospecific autoantibodies that generate a DFS-like or pseudo-DFS IFA pattern but do not react with DFS70/LEDGFp75. We characterized this pattern using confocal microscopy and immunoblotting. The target antigen associated with this pattern partially co-localized with DFS70/LEDGFp75 and its interacting partners H3K36me2, an active chromatin marker, and MLL, a transcription factor, in HEp-2 cells, suggesting a role in transcription. Immunoblotting did not reveal a common protein band immunoreactive with antibodies producing the pseudo-DFS pattern, suggesting they may recognize diverse proteins or conformational epitopes. Given the subjectivity of the HEp-2 IFA test, the awareness of pseudo-DFS autoantibodies reinforces recommendations for confirmatory testing when reporting patient antibodies producing a putative DFS pattern in a clinical setting. Future studies should focus on defining the potential diagnostic utility of the pseudo-DFS pattern and its associated antigen(s).

The LEDGF/p75 Integrase Binding Domain Interactome Contributes to the Survival, Clonogenicity, and Tumorsphere Formation of Docetaxel-Resistant Prostate Cancer Cells

Patients with prostate cancer (PCa) receiving docetaxel chemotherapy invariably develop chemoresistance. The transcription co-activator lens epithelium-derived growth factor p75 (LEDGF/p75), also known as DFS70 and PSIP1, is upregulated in several human cancers, including PCa and promotes resistance to docetaxel and other drugs. The C-terminal region of LEDGF/p75 contains an integrase binding domain (IBD) that tethers nuclear proteins, including the HIV-1 integrase and transcription factors, to active chromatin to promote viral integration and transcription of cellular survival genes. Here, we investigated the contribution of the LEDGF/p75 IBD interactome to PCa chemoresistance. Quantitative immunoblotting revealed that LEDGF/p75 and its IBD-interacting partners are endogenously upregulated in docetaxel-resistant PCa cell lines compared to docetaxel-sensitive parental cells. Using specific human autoantibodies, we co-immunoprecipitated LEDGF/p75 with its endogenous IBD-interacting partners JPO2, menin, MLL, IWS1, ASK1, and PogZ, as well as transcription factors c-MYC and HRP2, in docetaxel-resistant cells, and confirmed their nuclear co-localization by confocal microscopy. Depletion of LEDGF/p75 and selected interacting partners robustly decreased the survival, clonogenicity, and tumorsphere formation capacity of docetaxel-resistant cells. These results implicate the LEDGF/p75 IBD interactome in PCa chemoresistance and could lead to novel therapeutic strategies targeting this protein complex for the treatment of docetaxel-resistant tumors.